In early 2003, Glenn Carle, an interrogator with the CIA, arrived at a secret detention facility overseas to question a recently captured Al-Qaeda suspect. The jail, whose location remains classified, was cold and dark—so dark Carle could not see his own hands—and music blared loudly all around. Inside the cell, a man lay shivering under a flimsy blanket; Carle called to him, and he looked up slowly, weary and confused, when Carle entered. When questioned, the man could manage only a rambling, incoherent reply. “He was a wreck,” Carle says.

The man’s dilapidated state of mind was the result of a systematic program of torture inflicted on terrorism suspects by the CIA after 9/11. Nudity, extreme temperatures, sleep and sensory deprivation, dietary manipulation, waterboarding and other “enhanced interrogation techniques” were meant to break down detainees’ resistance to interrogation. The stress and disorientation induced by these methods, it was believed, would force them to cooperate and release whatever precious information they were hiding. But according to Carle, this theory is wrong.

“Information obtained under duress is suspect and polluted from the start and harder to verify,” he says.

His views have been vindicated by the Senate Select Committee on Intelligence, which concluded in the executive summary of its 6,000-page study of the CIA program, released in December 2014, that the agency’s harsh methods failed to glean any intelligence not available through softer tactics. However, the CIA has disputed the Senate’s findings, and Republican presidential candidate Donald Trump has vowed to reinstate torture if elected. Trump has been particularly raucous in his support for brutal interrogation, urging that Salah Abdeslam, apprehended as a suspect in the November 2015 attacks in Paris, be waterboarded.

Disorientation impairs memory

Meanwhile, compelling scientific evidence is emerging that torture and coercion are, at best, ineffective means of gathering intelligence. Worse, as Shane O’Mara, a professor of experimental brain research at Trinity College Dublin, wrote in a recent book, Why Torture Doesn’t Work: The Neuroscience of Interrogation, torture can produce false information by harming those areas of the brain associated with memory. O’Mara marshals a large amount of scientific literature to make his point. In one important experiment from 2006, psychiatrist Charles Morgan and colleagues subjected a group of special operations soldiers to prisoner-of-war conditions (including food and sleep deprivation and temperature extremes).

These soldiers were highly trained and physically fit, and, unlike most detainees, they were motivated to cooperate. But even they exhibited a remarkable deterioration in memory as a result of these stressful conditions. According to Carle, enhanced interrogation techniques have similar effects. “It is obvious that sleep deprivation and temperature extremes disorient the detainee—they are designed to do so,” he says.

“If one is disoriented, virtually by definition one’s memory is impaired. It is simply shocking one could be so stupid as to argue the opposite.”

Waterboarding was the CIA’s most notorious interrogation technique. In this procedure, a prisoner is strapped to a board, his face covered with a cloth. Water is gradually poured over the cloth until it fills the prisoner’s mouth and nasal cavity, preventing him from breathing. As he suffocates, panic and terror take hold, and it is assumed the prisoner will “talk” and tell the truth to be allowed to breathe.

Like other enhanced measures, waterboarding cannot be tested in a laboratory for ethical reasons, but there is a sizable amount of relevant scientific literature on it. As O’Mara shows in his book, studies of the “diving reflex” (a set of physiological responses that occur when mammals, including humans, are submerged in water) have demonstrated that immersion in cold water moves brain activity away from areas supporting memory to those “principally concerned with survival,” such as the brainstem and amygdala, which regulate fear, pain and stress. By occluding the airways, waterboarding starves people of air, and there is a “huge literature” showing that lack of oxygen (hypoxia) harms cognition, O’Mara tells Newsweek. He highlights one recent study, which found that hypoxia “severely impairs” a person’s cognitive abilities. Furthermore, waterboarding causes carbon dioxide to accumulate in the body (hypercapnia), which induces fear and panic. In this situation, the ability to think and recall information will be “markedly reduced,” he says.

Despite the abundance of evidence relevant to torture, O’Mara is the first brain scientist to write such a book. “I’ve genuinely been surprised by the silence,” he says. O’Mara and his colleagues at Trinity College Dublin are completing a research project that examines the effects of water immersion and breath-holding on memory. Participants are asked to lie down with a wet cloth over their face and hold their breath while their physiology is monitored; then they are asked to recall bits of previously learned information. The study is in its third round of experiments and must still undergo peer review, but the results so far seem to indicate that the process impairs memory.

A prisoner of war is interrogated in a detention center in Balad, Iraq on July 19, 2003, where prisoners are deprived of sleep using bright lights and loud heavy metal music. Rita Leistner/Redux

Indeed, the Navy’s Survival, Evasion, Resistance and Escape school used to subject U.S. soldiers to waterboarding as part of their resistance training (it stopped in 2007), and former instructor Malcolm Nance says the procedure does not elicit reliable information. It does, on the other hand, generate false confessions. “The captive will say absolutely anything and agree to anything to make the torture stop,” says Nance. Most of those subjected to waterboarding, he says, confess as a result—and their distress is so intense, they do not even remember confessing. In a recent BBC documentary, for which Nance served as a consultant, a volunteer underwent waterboarding and confessed to “being born a bunny rabbit.” He had no recollection of making such an admission.

Depriving detainees of sleep is also unlikely to help those trying to gather intelligence. A study published in Proceedings of the National Academy of Sciences earlier this year examined the effects of sleep deprivation on false confessions. Over 80 student volunteers were asked to complete a number of computer-based tasks. Beforehand, they were told that pressing the "escape" key on their computers would damage essential data. Having completed the tasks, the volunteers were then divided into two groups: One was allowed to sleep all night; the other had to stay awake. The following day, the students in both groups were asked to sign a statement admitting they had pressed the "escape" key during the tasks. Sleep-deprived participants were 4.5 times more likely to sign the false confession.

“This is a dramatic increase,” says Elizabeth Loftus, a professor of cognitive science and law at the University of California, Irvine, and one of the study’s authors. “It should alert people to the potential for false confessions” in cases of sleep deprivation. This is especially pertinent to the U.S. criminal justice system, Loftus says, where sleep deprivation is common and false confessions have featured in a disturbing number of wrongful convictions.

The caveat, says Kimberly Fenn, who runs the Sleep and Learning Lab at Michigan State University and was one of Loftus’s co-authors, is that their study does not ask participants to confess to an actual crime, so rates of false confession connected to sleep deprivation might be lower in the real world. Still, the work adds to a growing body of scientific literature suggesting sleep deprivation is not an effective interrogation technique. “Performance in a wide range of cognitive functions, including the ability to retrieve information from long-term memory, is impaired under sleep deprivation,” says Fenn.

An earlier project by the same team found that sleep loss could even lead to the formation of false memories. Sleeplessness can also induce psychosis—the Senate report describes a sleep-deprived detainee who experienced intense hallucinations, for example. Tony Camerino, a former senior interrogator with a special operations task force, saw sleep-deprived prisoners frequently during his time in Iraq in 2006. Sleep deprivation “absolutely” harms memory, he says, and “leads to inaccurate information.”

President Barack Obama officially stopped the CIA interrogation techniques by executive order in 2009, although the program had effectively ended before then. And a new law enacted last year requires all interrogations to comply with standards set down in the Army Field Manual, which prohibits waterboarding, prolonged sleep deprivation and other enhanced interrogation techniques. In an emailed statement, CIA spokesman Dean Boyd tells Newsweek, “It is CIA Director Brennan’s resolute intention to ensure that Agency officers scrupulously adhere to these directives, which the Director fully supports.” This unusually firm posture comes weeks after John Brennan told NBC that he would not obey orders to use waterboarding again and signals a newly defiant rejection of torture from the agency.

But, while enhanced interrogation is now banned, some coercive methods remain available. The manual contains a controversial appendix, which could allow for some coercive tactics, such as isolation or partial sleep and sensory deprivation. For example, it permits interrogators to restrict detainees to four hours of sleep every 24 hours over an indefinite period. And, according to Fenn and O’Mara, research indicates that partial sleep deprivation like this could be just as harmful as complete sleep loss. The appendix might be rescinded, though, as a new law mandates a thorough review of the manual, which is now underway and expected to be completed in a few years. The Department of Defense did not respond to Newsweek’s request for comment.

Viable alternatives

While torture is slowly but surely being excised from U.S. policy, new scientific research is suggesting more effective interrogation techniques. The High-Value Detainee Interrogation Group, or HIG, was set up by Obama in 2009 to conduct interrogations of high-profile terrorism suspects and sponsor research into effective interrogation techniques, and it has backed a considerable number of important new studies.

“The good news is that there is substantial research on viable alternatives that do not rely on coercion but instead on rapport building,” says Maria Hartwig, a psychology professor at John Jay College of Criminal Justice at the City University of New York, who has contributed to a number of HIG-funded projects. The new law requires the HIG to produce a report detailing “best practices for interrogation,” expected to be made public soon.

One research area backed by the HIG focuses on methods used by the World War II–era German interrogator Hanns Scharff, who adopted a friendly, subtle approach to interrogation, known as “information elicitation.” Instead of posing direct questions and pressing for details, Scharff pretended he already knew everything. That way, it was assumed, the detainee would deem it futile to withhold information. Scharff would slip details into casual conversation, which the detainee would then confirm or deny, unaware he was providing fresh intelligence.

Recent research has supported the efficacy of the Scharff technique. According to Pär-Anders Granhag, a professor of psychology at the University of Gothenburg in Sweden, these tactics have just been tested successfully on Norwegian policemen who handle informants. (The study is currently under review and not yet published.) Granhag says he and his colleagues are receiving “more and more” requests to train practitioners in the Scharff method. “So far, we have trained police units in Sweden and Norway, and the LAPD and FBI.”